Last year was full of changes within the practice of refractive surgery. A big one was the increase in the popularity of surface ablation. Why is this happening? It ties back to the most recent advances in technology and medication. Better blend zones and the use of mitomycin C for haze have made the procedure more viable. Its indications have also improved. We now know that patients with thin corneas, who may be predisposed to trauma, are better candidates for surface ablation rather than LASIK. Patients with filtering blebs, prior retinal detachment surgery, glaucoma, irregular corneas (flat or steep), and deep-set eyes also do much better with surface ablation. Moreover, there is the possibility that patients may achieve better visual results from surface ablation than LASIK because there are no flap-related aberrations. Most importantly, however, we surgeons now have a better understanding of the risks of ectasia, and it appears that, for many patients, surface ablation is safer than LASIK.
The bed of a flap made with the Intralase FS laser (Intralase Corp., Irvine, CA), or any lamellar flap, is not going to be nearly as regular as the bed of a keratome-made Epi-LASIK bed. A relatively simple technique, Epi-LASIK was one of the hot topics in 2005, and one my colleagues and I started exploring the technique.
There are several new epikeratomes that have recently become available. I like to use a microkeratome with an epikeratome blade, such as the Amadeus II (Advanced Medical Optics, Inc., Santa Ana, CA), that separates the epithelium from the underlying Bowman's membrane (Figure 1). Next, I return the epithelial layer to its original position while making certain it does not stretch in the process. I was able to create viable epithelial flaps in 38 of my first 40 cases. These patients underwent surface ablation but had a bandage lens of their own repositioned epithelium. They were much more comfortable than if they had undergone a standard PRK.
LAMELLAR EPITHELIAL DEBRIDEMENT
I have conducted two studies evaluating the efficacy of Epi-LASIK and lamellar epithelial debridement. Visual results were evaluated for 20 patients undergoing bilateral Epi-LASIK with the Amadeus II microkeratome. In one eye, the epithelial flap was removed (lamellar epithelial debridement), and, in the other eye, the epithelial flap was replaced (Epi-LASIK). These patients were evaluated and compared to 20 patients undergoing Epi-LASIK in one eye and manual PRK in the other eye.
My colleagues and I tracked the size of patients' postoperative epithelial defect by measuring it with a slit lamp and digitally photographing the wound daily until it healed. All patients received a standard postoperative drop regimen of Acular LS (Allergan, Inc., Irvine, CA), Pred Forte 1% (Allergan, Inc.), and Zymar (Allergan, Inc.) q.i.d., and they wore bandage contact lenses in both eyes for 4 days postoperatively (Figure 2).
Lamellar epithelial debridement is an advanced surgical technique. After removing the epithelial flap and discarding it, I performed a surface ablation. The result was a regular, smooth epithelial debridement and Bowman's layer. During the procedure, my colleagues and I used a blade oscillation speed of 11,000rpm, slowed the translation speed of the Amadeus II to 1.5mm per second, and reduced suction by approximately 10%. We created 9.5-mm epithelial flaps on all patients. During our examination of the histopathology of the epithelial flaps with light microscopy, we found viable cells, suggesting that if the epithelial flap were replaced the cells would be viable.
The concerns with surface ablation techniques relate to how much pain a patient will experience and how the pain associated with Epi-LASIK, lamellar epithelial debridement, or PRK procedures compares. The results of our study confirmed that the Epi-LASIK procedure was significantly comfortable of all three (P<.05). After Epi-LASIK, the epithelial flap acts like an amniotic membrane, covering the cornea, and thus provides greater comfort.
UCVA and BCVA
In our comparison of UCVA postoperatively, vision was not quite as good with Epi-LASIK or PRK as it was with lamellar epithelial debridement. The return of BCVA and UCVA was significantly faster with lamellar epithelial debridement than Epi-LASIK or PRK (P<.05). Removing the flap during lamellar epithelial debridement created a more rapid visual rehabilitation. Patients saw better and gained vision quicker if the flap was removed. BCVA followed the same course with a marked improvement in visual acuity.
The results of our study indicate that patients who undergo Epi-LASIK with lamellar epithelial debridement experienced a speedier recovery than those who underwent Epi-LASIK or PRK. Seventy-five percent of patients reported being able to return to work within 3 or 4 days after lamellar debridement, whereas those who underwent PRK or Epi-LASIK procedures required a mean of 1.5 days to recover. Epithelial defect is not an issue with Epi-LASIK. But, with lamellar epithelial treatment, epithelial defects closed more quickly because the defect is more regular and there is no damage to the peripheral epithelium. Perhaps our most striking finding was surface regularity following PRK and lamellar epithelial debridement. The classic epithelial suture line or healing ridge line that is almost always apparent in some form after PRK was rarely visible after lamellar epithelial debridement, again because of the regular borders of the epithelial defect and the symmetric healing pattern. Because of the regularity of its borders, the epithelium lies down far more smoothly, which allows for much more rapid visual rehabilitation.
I believe that the most critical event following surface ablation is prompt and predictable re-epithelialization. Delayed re-epithelialization increases the time for visual rehabilitation and the incidence of postoperative haze, pain, and photophobia as well as the risk of infectious keratitis. Mechanical separation without alcohol preserves the integrity of the epithelium and the stroma. It partners well with wavefront-guided customized ablations and may improve patients' comfort, the predictability of results, and patients' visual recovery.
Epi-LASIK with a microkeratome removes the entire corneal epithelial layer but causes no discernable damage to the removed tissue or to the underlying Bowman's membrane. The procedure provides greater patient comfort when compared with PRK or lamellar epithelial debridement; however, the latter provides speedier visual rehabilitation than PRK or Epi-LASIK. In Epi-LASIK the epithelial flap, which reduces discomfort, must be replaced or remodeled to produce a smooth ocular surface. This process delays the return of BCVA.
Eric D. Donnenfeld, MD, is a partner in Ophthalmic Consultants of Long Island and is Co-Chairman of Corneal and External Disease at the Manhattan Eye, Ear and Throat Hospital in New York. He is a paid consultant for Allergan, Inc., and for Advanced Medical Optics, Inc. Dr. Donnenfeld may be reached at (516) 766-2519; firstname.lastname@example.org.